Not Applicable
Not Applicable
Poke-thru fittings are designed to be installed in an opening in a floor, such as a concrete slab or steel deck, in a building structure such as an office building to provide electrical receptacles and/or communication/data receptacles at desired locations in buildings. As explained in U.S. Pat. No. 4,770,643, source power and signal cables, loosely positioned in a plenum, which is between the ceiling of the floor below and the floor above (that is, the floor in which the opening is in), may be pulled from the plenum and connected with or passed through the poke-thru fitting for activation of services for and on the floor above. More specifically, high voltage source power cables are connected with power receptacles that may be mounted within the poke-thru fitting or surface mounted on the floor above the fitting. Lower voltage communication/data signal cables have traditionally been passed through the poke-thru fitting to provide above floor connections between these cables and equipment positioned on the floor above. More recently, poke-thru fittings have been developed that also provide for mounting the communication/data receptacle within the fitting.
Standards promulgated by Underwriters Laboratories (UL) require poke-thru fittings to enable the fire rating of the floor to be substantially the same with or without the floor opening and fitting therein. As a result, poke-thru fittings typically incorporate fire-retarding material, generally intumescent material, to retard the transmission of heat and flame from a fire in the plenum, for example. The intumescent material is activated upon exposure to a fire""s heat and flames, rising through the floor opening from a fire below the floor. The intumescent material absorbs the heat and expands to fill open spaces in the floor.
Intumescent material, which is a hydrated compound, tends to age over time (that is, to become hardened by absorbing moisture or water). Poke-thru fittings are frequently used in new buildings having concrete floors. The moisture in the new concrete is a ready source of moisture for absorption by the intumescent material, which can result in undesirable aging of the intumescent material.
In the past, fire-retardant intumescent material have been made and stored in flat sheets. The sheets are cut into desired shapes for use in poke-thru fittings. These sheets are sandwiched between top and bottom layers of protective materials, but the cut, side edges of the intumescent material remain exposed since they are not covered by the protective layers. As a result, the sheet type intumescent material is proven to age due to moisture infiltration. In addition, the sheet form intumescent material is relatively flexible and therefore does not contribute significantly to the structural integrity of the fitting. The sheet form intumescent material is also cumbersome and time consuming to use during manufacturing because, for example, the large sheets of intumescent material must be stored, handled and cut into the desired configuration of incorporation into the fitting. A further drawback of the sheet form intumescent material is that it can only be used to form a limited number of structural geometries.
In response to moisture degradation problems associated with sheet form intumescent materials, U.S. Pat. No. 6,018,126, which is assigned to the assignee of the present invention, discloses encapsulating intumescent material with an composition, such as polyvinyl chloride (PVC), to protect the material against damage from high humidity and moisture and to retard premature aging and degredation. In implementation, this is accomplished by pouring the intumescent material into relatively thin-walled PVC cups or shells and then curing the intumescent material. This results in a relatively flexible intumescent insert that can be incorporated into the poke-thru assembly. However, because the intumescent insert of the ""126 patent is relatively flexible, it does not contribute significantly to the structural rigidity to the fitting. In addition, the manner in which these inserts are formed is somewhat cumbersome and time consuming. Further, both the inserts of the ""126 patent and the sheet form intumescent material can be compressed overtime resulting in a degreatation of the ground continuity of the fitting. For example, in the ""126 patent, intumescent inserts 50 are secured between plates 39 and 70 by a connector 82 which also serves as a path for ground continuity. If the intumescent inserts 50 become compressed over time, the connection between the plates 39, 70 and the connector 82 can loosen, resulting in degradation of the ground continuity of the fitting.
According to certain aspects of an embodiment of the present invention, a wiring fitting of the type adapted to be supported in a floor opening in a floor of a building structure. The fitting includes at least one intumescent fire retarding member formed from a polymeric based intumescent material. Employing a polymeric intumescent material allows the intumescent members to be formed by molding or extruding processes. A relatively rigid intumescent material may be used to form components including a tubular insert sized for insertion into the floor opening, as well as other components that could otherwise be formed from plastic, such as the cover plate, the receptacle barrier, and the trim flange. A relatively flexible polymeric based intumescent material can be used to form seals in the fitting.